This project proposes to investigate the interactions between T lymphocytes in the context of chronic inflammation and infection. The hypothesis is that B. burgdorferi infection activates the vascular endothelium, enhancing extravasation of T lymphocytes that secret type 1 proinflammatory cytokines. To test this central hypothesis, the PI will use in vitro models to pursue the following specific aims: 1) Determine the subpopulations of T lymphocytes that migrate across endothelium exposed to B. burgdorferi; 2) Identify the adhesion molecules and chemo-attractants involved in the migration of T lymphocytes across spirochete-stimulated endothelium; and 3) Explore the capacity of the host cytokine, interleukin (IL)10, to modulate interactions of T lymphocytes with endothelium activated by B. burgdorferi. These studies will provide greater insight into how accumulation of T lymphocytes is regulated not only in Lyme disease, but also in chronic inflammation in general.